Using cathode spacers to minimize reactor size in air cathode microbial fuel cells

Area of Science:

• Bioelectrochemical systems
• Renewable energy technologies
• Environmental engineering

Background:

• Scaling up microbial fuel cells (MFCs) necessitates compact reactor designs.
• Reactor size reduction is critical for the economic viability and practical application of MFCs.
• Optimizing reactor geometry can enhance MFC performance and efficiency.

Purpose of the Study:

• To investigate the impact of spacers on microbial fuel cell (MFC) reactor size and performance.
• To determine optimal spacer dimensions for maximizing power density and coulombic efficiency in MFCs.
• To assess the feasibility of using spacers for scalable MFC designs.

Main Methods:

• Fabrication and testing of MFCs with various spacer thicknesses (e.g., 1.3mm, 1.5mm).
• Measurement of maximum power density and coulombic efficiency under different spacer configurations.
• Analysis of oxygen transfer into the reactor based on spacer design and performance data.

Main Results:

• A 1.5mm expanded plastic spacer (S1.5) yielded a maximum power density (973±26mWm⁻²) comparable to MFCs without spacers.
• A 1.3mm spacer significantly reduced MFC power output by 33%.
• The S1.5 spacer increased coulombic efficiency from 20% to 24% by limiting oxygen ingress.

Conclusions:

• Spacers, particularly a 1.5mm thickness, can effectively minimize MFC reactor size without compromising power generation.
• Reduced oxygen transfer facilitated by optimal spacers enhances coulombic efficiency.
• Active airflow may be required for large-scale MFCs, with an estimated need of 0.9 Lh⁻¹ per m² of cathode area.